1. Field of the Invention:
This invention relates to apparatus for reproducing information from a tape-shaped recording medium which was run at two or more different speeds during recording. Such reproducing apparatus includes magnetic recording and reproducing apparatus, optical reproducing apparatus and many more various types of apparatus. However, the disclosed embodiments are directed chiefly to an apparatus for reproducing video informations from a magnetic tape on which television signals have been recorded, or a video tape recorder (hereinafter referred to as "VTR").
2. Description of the Prior Art:
Recently, high density magnetic recording has become possible, and VTRs capable of making long-time recordings and reproducing such recordings have been developed and commercially manufactured.
For adaption to the convention format too, these are made to operate at various selected time modes, for example, standard and long, during recording and reproduction in a single VTR item. To reproduce the picture recorded on the magnetic tape by such a dual time mode operating VTR, it is necessary to set up the same time mode as the recording operation. Otherwise, because of the tape format being different, a disturbed picture would be reproduced. Manually choosing the required reproduction time mode while observing the reproduced images is very inconvenient to the user. On this account, according to the prior art, when recording, the tape is given one control signal (hereinafter referred to as "CTL" signal) for every one frame at the vicinity thereof. Then when reproducing, the number of revolutions of the capstan motor proportional to the distance the magnetic tape has run is sensed with a pulse generator, and how many pulses have been produced in the time interval of occurrence of the CTL signal is counted to examine whether or not the time mode is different between the recording and the reproduction. Upon detection of the difference, the preliminary setting of the time mode is automatically changed.
Such prior art is described by way of example with reference to FIG. 1. A magnetic tape 1 is moved in a direction indicated by arrow by a capstan 2 and a pinch roller 3. Reproduced from the magnetic tape 1 is the video signal which has been recorded on the incline track to the length of the magnetic tape 1 by a rotating magnetic head (not shown) fixedly carried on a rotary drum as is well known in the art. The capstan 2 is driven by a motor 4 through an endless belt 5 to rotate at a prescribed speed. To sense the speed of rotation of the capstan motor 4, a frequency generator 6 whose output pulses are proportional in number to the speed of movement of the magnetic tape 1 are applied to a counter 8 at a clock input terminal CK thereof. A control head 9 picks up the CTL signals of repetition in frame unit, and its output is applied through an amplifier 10 and a waveform shaper 11 to the "reset" terminal R of the aforesaid counter 8. With such input stage, the counter 8 recycles counting of the number of pulses in a time interval from one to the next CTL signal and its outputs Q1 to Q4 are applied to a magnitude comparator 13 where they are compared with outputs of a reference control 12 in which a number is preset. When this reference number is exceeded, the output Q5 of comparator 13 assumes a high level. That is to say, for the standard mode, the number of pulses counter 8 has counted in between the successive two CTL signals is assumed to be 44. Then if the recording has been operated in the long time mode, where the tape speed is halved, the CTL time interval becomes 1/2 times that of the standard mode. Therefore, when the magnetic tape which has been run at the long time mode during recording is run at the standard mode during reproduction, the number of pulses counted in every one CTL interval is not 44 as normal, but only a half of that, or 22. With the reference control 12 having preset therein an intermediate number between 22 and 44, therefore, that no more than the reference number is counted during reproduction at the standard mode, shows that the recording has been operated in the long time mode. Conversely that more than the reference number is counted, shows that the recording was operated in the standard mode.
However, if some of the CTL signals have failed to be recorded, as if formats do not have what is called the control signals are employed, a problem arises because such automatic mode setting does not result.